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Date: Mon, 14 Nov 2022 14:51:06 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Thomas Kupper <thomas@...per.org>, netdev@...r.kernel.org,
"S-k, Shyam-sundar" <Shyam-sundar.S-k@....com>
Cc: Jakub Kicinski <kuba@...nel.org>,
Raju Rangoju <Raju.Rangoju@....com>
Subject: Re: [PATCH v2 net 1/1] amd-xgbe: fix active cable
On 11/14/22 13:20, Thomas Kupper wrote:
> On 11/14/22 18:39, Tom Lendacky wrote:
>> On 11/12/22 13:12, Thomas Kupper wrote:
>>> On 11/11/22 17:00, Thomas Kupper wrote:
>>>> On 11/11/22 15:18, Tom Lendacky wrote:
>>>>> On 11/11/22 02:46, Thomas Kupper wrote:
>>>>>> When determine the type of SFP, active cables were not handled.
>>>>>>
>>>>>> Add the check for active cables as an extension to the passive cable check.
>>>>>
>>>>> Is this fixing a particular problem? What SFP is this failing for? A more descriptive commit message would be good.
>>>>>
>>>>> Also, since an active cable is supposed to be advertising it's capabilities in the eeprom, maybe this gets fixed via a quirk and not a general check this field.
>>>
>>> Tom,
>>>
>>> are you sure that an active cable has to advertising it's speed? Searching for details about it I read in "SFF-8472 Rev 12.4", 5.4.2, Table 5-5 Transceiver Identification Examples:
>>>
>>> Transceiver Type Transceiver Description Byte Byte Byte Byte Byte Byte Byte Byte
>>> 3 4 5 6 7 8 9 10
>>> ...
>>> 10GE Active cable with SFP(3,4) 00h 00h 00h 00h 00h 08h 00h 00h
>>>
>>> And footnotes:
>>> 3) See A0h Bytes 60 and 61 for compliance of these media to industry electrical specifications
>>> 4) For Ethernet and SONET applications, rate capability of a link is identified in A0h Byte 12 [nominal signaling
>>> rate identifier]. This is due to no formal IEEE designation for passive and active cable interconnects, and lack
>>> of corresponding identifiers in Table 5-3.
>>>
>>> Wouldn't that suggest that byte 3 to 10 are all zero, except byte 8?
>>
>> This issue seems to be from my misinterpretation of active vs passive.
>> IIUC now, active and passive only applies to copper cables with SFP+ end
>> connectors. In which case the driver likely needs an additional enum cable
>> type, XGBE_SFP_CABLE_FIBER, as the default cable type and slightly
>> different logic.
>>
>> Can you try the below patch? If it works, I'll work with Shyam to do some
>> testing to ensure it doesn't break anything.
>
> Thanks Tom for getting back to me so soon.
>
> Your patch works well for me, with a passive, an active cable and a GBIC.
>
> But do you think it's a good idea to just check for != XGBE_SFP_CABLE_FIBER? That would also be true for XGBE_SFP_CABLE_UNKNOWN.
Except the if-then-else block above will set the cable type to one of the
three valid values, so this is ok.
I'll work with Shyam to do some internal testing and get a patch sent up
if everything looks ok on our end.
Thanks,
Tom
>
> /* Determine the type of SFP */
> - if (phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE &&
> + if (phy_data->sfp_cable != XGBE_SFP_CABLE_FIBER &&
> xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
> phy_data->sfp_base = XGBE_SFP_BASE_10000_CR;
> else if (sfp_base[XGBE_SFP_BASE_10GBE_CC] & XGBE_SFP_BASE_10GBE_CC_SR)
>
> Cheers
> Thomas
>
>>
>>
>> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> index 4064c3e3dd49..868a768f424c 100644
>> --- a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>> @@ -189,6 +189,7 @@ enum xgbe_sfp_cable {
>> XGBE_SFP_CABLE_UNKNOWN = 0,
>> XGBE_SFP_CABLE_ACTIVE,
>> XGBE_SFP_CABLE_PASSIVE,
>> + XGBE_SFP_CABLE_FIBER,
>> };
>>
>> enum xgbe_sfp_base {
>> @@ -1149,16 +1150,18 @@ static void xgbe_phy_sfp_parse_eeprom(struct xgbe_prv_data *pdata)
>> phy_data->sfp_tx_fault = xgbe_phy_check_sfp_tx_fault(phy_data);
>> phy_data->sfp_rx_los = xgbe_phy_check_sfp_rx_los(phy_data);
>>
>> - /* Assume ACTIVE cable unless told it is PASSIVE */
>> + /* Assume FIBER cable unless told otherwise */
>> if (sfp_base[XGBE_SFP_BASE_CABLE] & XGBE_SFP_BASE_CABLE_PASSIVE) {
>> phy_data->sfp_cable = XGBE_SFP_CABLE_PASSIVE;
>> phy_data->sfp_cable_len = sfp_base[XGBE_SFP_BASE_CU_CABLE_LEN];
>> - } else {
>> + } else if (sfp_base[XGBE_SFP_BASE_CABLE] & XGBE_SFP_BASE_CABLE_ACTIVE) {
>> phy_data->sfp_cable = XGBE_SFP_CABLE_ACTIVE;
>> + } else {
>> + phy_data->sfp_cable = XGBE_SFP_CABLE_FIBER;
>> }
>>
>> /* Determine the type of SFP */
>> - if (phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE &&
>> + if (phy_data->sfp_cable != XGBE_SFP_CABLE_FIBER &&
>> xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
>> phy_data->sfp_base = XGBE_SFP_BASE_10000_CR;
>> else if (sfp_base[XGBE_SFP_BASE_10GBE_CC] & XGBE_SFP_BASE_10GBE_CC_SR)
>>
>>>
>>>
>>> /Thomas
>>>
>>>>
>>>> It is fixing a problem regarding a Mikrotik S+AO0005 AOC cable (we were in contact back in Feb to May). And your right I should have been more descriptive in the commit message.
>>>>
>>>>>>
>>>>>> Fixes: abf0a1c2b26a ("amd-xgbe: Add support for SFP+ modules")
>>>>>> Signed-off-by: Thomas Kupper <thomas.kupper@...il.com>
>>>>>> ---
>>>>>> ??drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c | 5 +++--
>>>>>> ??1 file changed, 3 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>>>>>> index 4064c3e3dd49..1ba550d5c52d 100644
>>>>>> --- a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>>>>>> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
>>>>>> @@ -1158,8 +1158,9 @@ static void xgbe_phy_sfp_parse_eeprom(struct xgbe_prv_data *pdata)
>>>>>> ????? }
>>>>>>
>>>>>> ????? /* Determine the type of SFP */
>>>>>> -??? if (phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE &&
>>>>>> -??? ??? xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
>>>>>> +??? if ((phy_data->sfp_cable == XGBE_SFP_CABLE_PASSIVE ||
>>>>>> +??? ???? phy_data->sfp_cable == XGBE_SFP_CABLE_ACTIVE) &&
>>>>>> +??? ???? xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
>>>>>
>>>>> This is just the same as saying:
>>>>>
>>>>> ????if (xgbe_phy_sfp_bit_rate(sfp_eeprom, XGBE_SFP_SPEED_10000))
>>>>>
>>>>> since the sfp_cable value is either PASSIVE or ACTIVE.
>>>>>
>>>>> I'm not sure I like fixing whatever issue you have in this way, though. If anything, I would prefer this to be a last case scenario and be placed at the end of the if-then-else block. But it may come down to applying a quirk for your situation.
>>>>
>>>> I see now that this cable is probably indeed not advertising its capabilities correctly, I didn't understand what Shyam did refer to in his mail from June 6.
>>>>
>>>> Unfortunately I haven't hear back from you guys after June 6 so I tried to fix it myself ... but do lack the knowledge in that area.
>>>>
>>>> A quirk seems a good option.
>>>>
>>>> From my point of view this patch can be cancelled/aborted/deleted.
>>>> I'll look into how to fix it using a quirk but maybe I'm not the hest suited candidate to do it.
>>>>
>>>> /Thomas
>>>>
>>>>>
>>>>> Thanks,
>>>>> Tom
>>>>>
>>>>>> ????? ??? phy_data->sfp_base = XGBE_SFP_BASE_10000_CR;
>>>>>> ????? else if (sfp_base[XGBE_SFP_BASE_10GBE_CC] & XGBE_SFP_BASE_10GBE_CC_SR)
>>>>>> ????? ??? phy_data->sfp_base = XGBE_SFP_BASE_10000_SR;
>>>>>> --
>>>>>> 2.34.1
>>>>>>
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